Massive ovarian edema is a rare tumor-like condition found in young women resulting from accumulation of fluid mostly due to partial or intermittent torsion of the ovary or secondary, to a preexisting ovarian lesion. We report a case of a 13-year-old girl presenting with an ovarian mass measuring 16 cm. CA-12-5 levels were slightly elevated. Concerns regarding underlying malignancy led to salpingo-oophorectomy. Pathological evaluation revealed a massive ovarian edema and multiple thromboses of ovarian veins. Differentiating massive ovarian edema from malignant ovarian tumor is crucial to prevent patients from undergoing unnecessary surgery.